1. Field of the Invention
The present invention relates to an internal combustion engine, and more particularly to a water temperature correction device and method thereof for an engine adapted to accurately control an internal combustion engine by correcting a characteristic curve of water temperature when the temperature of detected cooling water is high as compared to a reference value.
2. Description of the Prior Art
Generally, one of the most essential parameters in the control of an internal combustion engine is the temperature of cooling water. The temperature of cooling water detected by a water temperature sensor is input to a correction device according to a control signal output from the microcomputer.
Information representing the water temperature input to the correction device is used for various controls necessary for driving an internal combustion engine such as ignition time control, idle speed control, fuel injection control and the like.
FIG. 4 is an interface circuit diagram of a correction device for detecting a temperature of cooling water according to the prior art, where the information detected by the water temperature sensor passes a first resistor (R5) used as 5V pull-up resistor via an RC filter 24 comprising a second resistor (R7) and a first capacitor (C1) to be input to a microcomputer after being filtered, and is controlled by a previously set-up program.
At this point, the water temperature information from the water temperature sensor has a water temperature sensor characteristic curve, as illustrated in FIG. 5, and is stored in a memory of the correction device at a map table.
However, there is a problem in that the 5V pull-up resistor at the interface circuit for receiving the water temperature information detected by the water temperature sensor is fixed at a predetermined value, such that the detected water temperature has a wide width in water temperature change when the water temperature is high, whereas the detected voltage value is small. Thus, it is impossible to accurately control of the internal combustion engine by external influence.